sandbox/ghigo/src/test-particle/sphere-settling-large-domain.c

    Settling sphere in a large container at Re = 41

    This test case is based on the numerical work of Uhlman, 2005 and the experimental work of Mordant et al., 2000. We investigate the settling of a sphere of diameter D in a large domain, with parameters corresponding to case 1 in Mordant et al., 2000.

    This test case is governed by the Reynolds number Re = \frac{UD}{\nu}, where U is the “steady” settling velocity, and the Stokes number St= 1/9 Re \rho_p/\rho.

    We solve here the 3D Navier-Stokes equations and describe the sphere using an embedded boundary.

    #include "grid/octree.h"
#include "../myembed.h"
#include "../mycentered.h"
#include "../myembed-particle.h"
#include "../myperfs.h"
#include "lambda2.h"
#include "view.h"

    Reference solution

    #define d    (2./12.)
#define grav (9.81) // Gravity

#if RE == 1 // Re = 360
#define nu   (0.00104238) // Viscosity
#elif RE == 2 // Re = 280
#define nu   (0.00267626) // Viscosity
#else // Re = 41
#define nu   (0.005416368) // Viscosity
#endif // RE

#define uref (sqrt ((d)*(grav))) // Characteristic speed
#define tref (sqrt ((d)/(grav))) // Characteristic time

    We also define the shape of the domain.

    #define sphere(x,y,z) (sq ((x)) + sq ((y)) + sq ((z)) - sq ((d)/2.))

void p_shape (scalar c, face vector f, coord p)
{
  vertex scalar phi[];
  foreach_vertex() {
    phi[] = HUGE;
    for (double xp = -(L0); xp <= (L0); xp += (L0))
      for (double yp = -(L0); yp <= (L0); yp += (L0))
	for (double zp = -(L0); zp <= (L0); zp += (L0))
	  phi[] = intersection (phi[],
				(sphere ((x + xp - p.x),
					 (y + yp - p.y),
					 (z + zp - p.z))));
  }
  boundary ({phi});
  fractions (phi, c, f);
  fractions_cleanup (c, f,
		     smin = 1.e-14, cmin = 1.e-14);
}

    We finally define the particle parameters.

    #if RE == 2 // Re = 280
const double p_r = (7.71); // Ratio of solid and fluid density
const coord  p_i = {(p_moment_inertia_sphere ((d), 7.71)),
		    (p_moment_inertia_sphere ((d), 7.71)),
		    (p_moment_inertia_sphere ((d), 7.71))}; // Particle moment of interia
#else // RE = 41 and 360
const double p_r = (2.56); // Ratio of solid and fluid density
const coord  p_i = {(p_moment_inertia_sphere ((d), 2.56)),
		    (p_moment_inertia_sphere ((d), 2.56)),
		    (p_moment_inertia_sphere ((d), 2.56))}; // Particle moment of interia
#endif // RE
const double p_v = (p_volume_sphere ((d))); // Particle volume
const coord  p_g = {0., -(grav), 0.};

    Setup

    We need a field for viscosity so that the embedded boundary metric can be taken into account.

    face vector muv[];

    We define the mesh adaptation parameters and vary the maximum level of refinement.

    #define lmin (9) // Min mesh refinement level (l=9 is 2.5pt/d)
#if LMAX // 11, 12, 13, 14
#define lmax ((int) (LMAX))
#else // 12
#define lmax (12) // Max mesh refinement level (l=12 is 21pt/d)
#endif // LMAX
#define cmax (5.e-3*(uref)) // Absolute refinement criteria for the velocity field

int main ()
{

    The domain is 32^3. It needs to be sufficiently big to allow for long settling times without the particle reaching the bottom.

      L0 = 32.;
  size (L0);
  origin (-L0/2., 0., -L0/2.);

    We set the maximum timestep.

      DT = 1.e-3*(tref);

    We set the tolerance of the Poisson solver.

      TOLERANCE    = 1.e-4;
  TOLERANCE_MU = 1.e-4*(uref);

    We initialize the grid.

      N = 1 << (lmin); // todo: check the influence of coarser grid
  init_grid (N);
  
  run();
}

    Boundary conditions

    We use no-slip boundary conditions.

    u.n[left] = dirichlet (0);
u.t[left] = dirichlet (0);
u.r[left] = dirichlet (0);

u.n[right] = dirichlet (0);
u.t[right] = dirichlet (0);
u.r[right] = dirichlet (0);

u.n[bottom] = dirichlet (0);
u.t[bottom] = dirichlet (0);
u.r[bottom] = dirichlet (0);

u.n[top] = dirichlet (0);
u.t[top] = dirichlet (0);
u.r[top] = dirichlet (0);

u.n[back] = dirichlet (0);
u.t[back] = dirichlet (0);
u.r[back] = dirichlet (0);

u.n[front] = dirichlet (0);
u.t[front] = dirichlet (0);
u.r[front] = dirichlet (0);

    We give boundary conditions for the face velocity to “potentially” improve the convergence of the multigrid Poisson solver.

    uf.n[left]   = 0;
uf.n[right]  = 0;
uf.n[bottom] = 0;
uf.n[top]    = 0;
uf.n[back]   = 0;
uf.n[front]  = 0;

    Properties

    event properties (i++)
{
  foreach_face()
    muv.x[] = (nu)*fm.x[];
  boundary ((scalar *) {muv});
}

    Initial conditions

    event init (i = 0)
{

    We set the viscosity field in the event properties.

      mu = muv;

    We use “third-order” face flux interpolation.

    #if ORDER2
  for (scalar s in {u, p, pf})
    s.third = false;
#else
  for (scalar s in {u, p, pf})
    s.third = true;
#endif // ORDER2

    We use a slope-limiter to reduce the errors made in small-cells.

    #if SLOPELIMITER
  for (scalar s in {u, p, pf}) {
    s.gradient = minmod2;
  }
#endif // SLOPELIMITER  
  
#if TREE

    When using TREE and in the presence of embedded boundaries, we should also define the gradient of u at the cell center of cut-cells.

    #endif // TREE

    As we are computing an equilibrium solution when the particle reaches its settling velocity, we remove the Neumann pressure boundary condition which is responsible for instabilities.

    #if PNEUMANN // Non-zero Neumann bc for pressure
  for (scalar s in {p, pf}) {
    s.neumann_zero = false;
  }
#else // Zero Neumann bc for pressure
  for (scalar s in {p, pf}) {
    s.neumann_zero = true;
  }
#endif // PNEUMANN

    If the simulation is not restarted, we define the initial mesh and the initial velocity.

      if (!restore (file = "restart")) { // No restart

    We initialize the embedded boundary.

    We first define the particle’s initial position.

        p_p.y = (L0) - 5.*(d);
  
#if TREE

    When using TREE, we refine the mesh around the embedded boundary.

        astats ss;
    int ic = 0;
    do {
      ic++;
      p_shape (cs, fs, p_p);
      ss = adapt_wavelet ({cs}, (double[]) {1.e-30},
			  maxlevel = (lmax), minlevel = (1));
    } while ((ss.nf || ss.nc) && ic < 100);
#endif // TREE
  
    p_shape (cs, fs, p_p);
  }

    If the simulation is restarted, the proper restarting operations are performed in myembed-moving.h.

    }

    Embedded boundaries

    Adaptive mesh refinement

    #if TREE
event adapt (i++)
{
  adapt_wavelet ({cs,u}, (double[]) {1.e-2,(cmax),(cmax),(cmax)},
  		 maxlevel = (lmax), minlevel = (1));

    We do not need here to reset the embedded fractions to avoid interpolation errors on the geometry as the is already done when moving the embedded boundaries. It might be necessary to do this however if surface forces are computed around the embedded boundaries.

    }
#endif // TREE

    Restarts and dumps

    Every few characteristic time, we also dump the fluid data for post-processing and restarting purposes.

    #if DUMP
event dump_data (t += 5.*(tref))
{
  // Dump fluid
  char name [80];
  sprintf (name, "dump-level-%d-t-%g", (lmax), t/(tref));
  dump (name);

  // Dump particle
  char p_name [80];
  sprintf (p_name, "p_dump-level-%d-t-%g", (lmax), t/(tref));
  particle pp = {p_p, p_u, p_w, p_au, p_aw};
  struct p_Dump pp_Dump = {p_name, &pp};
  p_dump (pp_Dump);
}
#endif // DUMP

event dump_end (t = end)
{
  // Dump fluid
  char name [80];
  sprintf (name, "dump-level-%d-final", (lmax));
  dump (name);

  // Dump particle
  char p_name [80];
  sprintf (p_name, "p_dump-level-%d-final", (lmax));
  particle pp = {p_p, p_u, p_w, p_au, p_aw};
  struct p_Dump pp_Dump = {p_name, &pp};
  p_dump (pp_Dump);
}

    Profiling

    #if TRACE > 1
event profiling (i += 20) {
  static FILE * fp = fopen ("profiling", "a"); // In case of restart
  trace_print (fp, 1); // Display functions taking more than 1% of runtime.
}
#endif // TRACE

    Outputs

    event coeffs (i++; t < 75.*(tref))
{
  char name1[80];
  sprintf (name1, "level-%d.dat", lmax);
  static FILE * fp = fopen (name1, "a"); // In case of restart
  fprintf (fp, "%d %g %g %d %d %d %d %d %d %g %g %g %g %g %g %g %g %g %g %g %g\n",
	   i, t/(tref), dt/(tref),
	   mgp.i, mgp.nrelax, mgp.minlevel,
	   mgu.i, mgu.nrelax, mgu.minlevel,
	   mgp.resb, mgp.resa,
	   mgu.resb, mgu.resa,
	   p_p.x, p_p.y, p_p.z,
	   p_u.x/(uref), p_u.y/(uref), p_u.z/(uref),
	   fabs(p_u.y)*(d)/(nu), 1./9.*fabs(p_u.y)*(d)/(nu)*(p_r)
	   );
  fflush (fp);

  double cell_wall = fabs (p_p.y - (d)/2.)/((L0)/(1 << (lmax)));
  if (cell_wall <= 1.)
    return 1; // stop
}

event logfile (t = end)
{
  fprintf (stderr, "%d %g %g %d %d %d %d %d %d %g %g %g %g %g %g %g %g %g %g %g %g\n",
	   i, t/(tref), dt/(tref),
	   mgp.i, mgp.nrelax, mgp.minlevel,
	   mgu.i, mgu.nrelax, mgu.minlevel,
	   mgp.resb, mgp.resa,
	   mgu.resb, mgu.resa,
	   p_p.x, p_p.y, p_p.z,
	   p_u.x/(uref), p_u.y/(uref), p_u.z/(uref),
	   fabs(p_u.y)*(d)/(nu), 1./9.*fabs(p_u.y)*(d)/(nu)*(p_r)
	   );
  fflush (stderr);
}

    Snapshots

    event snapshots (t += 5.*(tref))
{
  scalar l2[];
  lambda2 (u, l2);

  scalar omega[];
  vorticity (u, omega); // Vorticity in xy plane

  char name2[80];

  clear();
  view (fov = 3, //theta = t/(4.*(tref)) - 0.5,
	tx = 0., ty = -(p_p.y + 4.*(d))/(L0),
	bg = {0.3,0.4,0.6},
	width = 800, height = 800);

  draw_vof ("cs", "fs");
  isosurface ("l2", -0.1, color = "omega", map = cool_warm);
  sprintf (name2, "l2-1em1-level-%d-t-%g.png", lmax, t/(tref));
  save (name2);
  
  draw_vof ("cs", "fs");
  isosurface ("l2", -0.01, color = "omega", map = cool_warm);
  sprintf (name2, "l2-1em2-level-%d-t-%g.png", lmax, t/(tref));
  save (name2);

  draw_vof ("cs", "fs");
  isosurface ("l2", -0.001, color = "omega", map = cool_warm);
  sprintf (name2, "l2-1em3-level-%d-t-%g.png", lmax, t/(tref));
  save (name2);
}
    gnuplot: warning: Cannot find or open file “level-12.dat”
    gnuplot: warning: Cannot find or open file “level-13.dat”

    Animations

    event movie (i += 250)
{
  scalar l2[];
  lambda2 (u, l2);

  scalar omega[];
  vorticity (u, omega); // Vorticity in xy plane

  char name2[80];

  clear();
  view (fov = 3, theta = t/(4.*(tref)) - 0.5,
	tx = 0., ty = -(p_p.y + 4.*(d))/(L0),
	bg = {0.3,0.4,0.6},
	width = 800, height = 800);
  
  draw_vof ("cs", "fs");
  isosurface ("l2", -0.1, color = "omega", map = cool_warm);
    gnuplot: warning: Cannot find or open file “case-0/level-11.dat”
    gnuplot: warning: Cannot find or open file “case-0/level-12.dat”
    gnuplot: warning: Cannot find or open file “case-0/level-13.dat” 
      sprintf (name2, "l2-1em1-level-%d.mp4", lmax);
  save (name2);

  draw_vof ("cs", "fs");
  isosurface ("l2", -0.01, color = "omega", map = cool_warm);
  sprintf (name2, "l2-1em2-level-%d.mp4", lmax);
  save (name2);

  draw_vof ("cs", "fs");
    gnuplot: warning: Cannot find or open file “case-0/level-11.dat”
    gnuplot: warning: Cannot find or open file “case-0/level-12.dat”
    gnuplot: warning: Cannot find or open file “case-0/level-13.dat”
    gnuplot: No data in plot 
      isosurface ("l2", -0.001, color = "omega", map = cool_warm);
  sprintf (name2, "l2-1em3-level-%d.mp4", lmax);
  save (name2);
}

    Results for Ga = 49.14

    \lambda_2

    \lambda_2 = -0.1 isosurface for l=11

    \lambda_2 = -0.01 isosurface for l=11

    \lambda_2 = -0.001 isosurface for l=11

    Settling velocity

    We plot the time evolution of the ratio of the computed and analytic settling velocities. We compare our results to the experimental results of cases 1,2 and 4 from Mordant et al., 2000.

    set terminal svg font ",16"
set key font ",10" top right spacing 0.7
set xlabel "t/t_{ref}"
set ylabel "u_{p,y}/u_{ref}"
set xrange [0:40]
set yrange [-4:1]

#Exponential fit from Mordant et al., 2000
f0(x) = -0.0741/sqrt(0.0005*9.81)*(1. - exp(-3*x*sqrt(0.0005/9.81)/0.055));

plot f0(x) w l lw 2 lc rgb "black" t "Mordant et al., 2000, Ga=49.14", \
     "level-12.dat" u 2:18 w l lw 2 lc rgb "blue"  t "Basilisk, l=12"

    Time evolution of the settling velocity $u_ (script){p,y}

    Results on supercomputer (cedar)

    Settling velocity for Ga = 49.14

    We plot the time evolution of the ratio of the computed and analytic settling velocities. We compare our results to the experimental results of case 1 from Mordant et al., 2000.

    reset
set terminal svg font ",16"
set xlabel "t/t_{ref}"
set ylabel "u_{p,y}/u_{ref}"
set xrange [0:40]
set yrange [-1.5:0]

#Exponential fit from Mordant et al., 2000
f0(x) = -0.0741/sqrt(0.0005*9.81)*(1. - exp(-3*x*sqrt(0.0005/9.81)/0.055));

plot f0(x) w l lw 2 lc rgb "black" t "Mordant et al., 2000, Ga=49.14", \
     "case-0/lmax-12/level-12.dat" u 2:18 w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-0/lmax-13/level-13.dat" u 2:18 w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-0/lmax-14/level-14.dat" u 2:18 w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the settling velocity $u_ (script){p,y}

    set key font ",16" top right spacing 1.1
set ylabel "u_{p,x}/u_{ref}"
set yrange [-1:1]
plot "case-0/lmax-12/level-12.dat" u 2:17 w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-0/lmax-13/level-13.dat" u 2:17 w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-0/lmax-14/level-14.dat" u 2:17 w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the velocity $u_ (script){p,x}

    set ylabel "u_{p,z}/u_{ref}"
plot "case-0/lmax-12/level-12.dat" u 2:19 w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-0/lmax-13/level-13.dat" u 2:19 w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-0/lmax-14/level-14.dat" u 2:19 w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the velocity $u_ (script){p,y}

    set ylabel "sqrt(u_{p,x}^2 + u_{p,z}^2)/u_{ref}"
plot "case-0/lmax-12/level-12.dat" u 2:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-0/lmax-13/level-13.dat" u 2:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-0/lmax-14/level-14.dat" u 2:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the velocity $(script){u_{p,x}

    set xlabel "u_{p,y}"
set ylabel "sqrt(u_{p,x}^2 + u_{p,z}^2)/u_{ref}"
set xrange [*:*]
set yrange [*:*]
plot "case-0/lmax-12/level-12.dat" u 18:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-0/lmax-13/level-13.dat" u 18:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-0/lmax-14/level-14.dat" u 18:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"
    Phase diagram of the vertical and horizontal velocities (script)

    Phase diagram of the vertical and horizontal velocities (script)

    set xlabel "x"
set ylabel "z"
set zlabel "y"
set xyplane 0
set xrange [-5:2]
set yrange [-5:5]
set zrange [0:*]
splot "case-0/lmax-12/level-12.dat" u 14:16:(-($15-32)) w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
      "case-0/lmax-13/level-13.dat" u 14:16:(-($15-32)) w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
      "case-0/lmax-14/level-14.dat" u 14:16:(-($15-32)) w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"
    Time evolution of the particle trajectory (script)

    Time evolution of the particle trajectory (script)

    Settling velocity for Ga = 255.35

    We plot the time evolution of the ratio of the computed and analytic settling velocities. We compare our results to the experimental results of case 2 from Mordant et al., 2000.

    reset
set terminal svg font ",16"
set xlabel "t/t_{ref}"
set ylabel "u_{p,y}/u_{ref}"
set xrange [0:40]
set yrange [-2.5:0]

#Exponential fit from Mordant et al., 2000
f1(x) = -0.218/sqrt(0.0015*9.81)*(1. - exp(-3*x*sqrt(0.0015/9.81)/0.142));

plot f1(x) w l lw 2 lc rgb "black" t "Mordant et al., 2000, Ga=255.35", \
     "case-1/lmax-12/level-12.dat" u 2:18 w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-1/lmax-13/level-13.dat" u 2:18 w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-1/lmax-14/level-14.dat" u 2:18 w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the settling velocity $u_ (script){p,y}

    set ylabel "u_{p,x}/u_{ref}"
set yrange [-1:1]
plot "case-1/lmax-12/level-12.dat" u 2:17 w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-1/lmax-13/level-13.dat" u 2:17 w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-1/lmax-14/level-14.dat" u 2:17 w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the velocity $u_ (script){p,x}

    set ylabel "u_{p,z}/u_{ref}"
plot "case-1/lmax-12/level-12.dat" u 2:19 w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-1/lmax-13/level-13.dat" u 2:19 w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-1/lmax-14/level-14.dat" u 2:19 w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the velocity $u_ (script){p,y}

    set ylabel "sqrt(u_{p,x}^2 + u_{p,z}^2)/u_{ref}"
plot "case-1/lmax-12/level-12.dat" u 2:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-1/lmax-13/level-13.dat" u 2:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-1/lmax-14/level-14.dat" u 2:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the velocity $(script){u_{p,x}

    set xlabel "u_{p,y}"
set ylabel "sqrt(u_{p,x}^2 + u_{p,z}^2)/u_{ref}"
set xrange [-2:-1.6]
set yrange [*:*]
plot "case-1/lmax-12/level-12.dat" u 18:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-1/lmax-13/level-13.dat" u 18:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-1/lmax-14/level-14.dat" u 18:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"
    Phase diagram of the vertical and horizontal velocities (script)

    Phase diagram of the vertical and horizontal velocities (script)

    set xlabel "x"
set ylabel "z"
set zlabel "y"
set xyplane 0
set xrange [-5:2]
set yrange [-5:5]
set zrange [0:*]
splot "case-1/lmax-12/level-12.dat" u 14:16:(-($15-32)) w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
      "case-1/lmax-13/level-13.dat" u 14:16:(-($15-32)) w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
      "case-1/lmax-14/level-14.dat" u 14:16:(-($15-32)) w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"
    Time evolution of the particle trajectory (script)

    Time evolution of the particle trajectory (script)

    Settling velocity for Ga = 206.27

    We plot the time evolution of the ratio of the computed and analytic settling velocities. We compare our results to the experimental results of case 3 from Mordant et al., 2000.

    reset
set terminal svg font ",16"
set xlabel "t/t_{ref}"
set ylabel "u_{p,y}/u_{ref}"
set xrange [0:40]
set yrange [-4.5:0]


#Exponential fit from Mordant et al., 2000
f1(x) = -0.316/sqrt(0.0008*9.81)*(1. - exp(-3*x*sqrt(0.0008/9.81)/0.108));

plot f1(x) w l lw 2 lc rgb "black" t "Mordant et al., 2000, Ga=206.27", \
     "case-2/lmax-12/level-12.dat" u 2:18 w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-2/lmax-13/level-13.dat" u 2:18 w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-2/lmax-14/level-14.dat" u 2:18 w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the settling velocity $u_ (script){p,y}

    set ylabel "u_{p,x}/u_{ref}"
set yrange [-1:1]
plot "case-2/lmax-12/level-12.dat" u 2:17 w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-2/lmax-13/level-13.dat" u 2:17 w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-2/lmax-14/level-14.dat" u 2:17 w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the velocity $u_ (script){p,x}

    set ylabel "u_{p,z}/u_{ref}"
plot "case-2/lmax-12/level-12.dat" u 2:19 w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-2/lmax-13/level-13.dat" u 2:19 w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-2/lmax-14/level-14.dat" u 2:19 w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the velocity $u_ (script){p,y}

    set ylabel "sqrt(u_{p,x}^2 + u_{p,z}^2)/u_{ref}"
plot "case-2/lmax-12/level-12.dat" u 2:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-2/lmax-13/level-13.dat" u 2:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-2/lmax-14/level-14.dat" u 2:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"

    Time evolution of the velocity $(script){u_{p,x}

    set xlabel "u_{p,y}"
set ylabel "sqrt(u_{p,x}^2 + u_{p,z}^2)/u_{ref}"
set xrange [-4:-3]
set yrange [*:*]
plot "case-2/lmax-12/level-12.dat" u 18:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
     "case-2/lmax-13/level-13.dat" u 18:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
     "case-2/lmax-14/level-14.dat" u 18:(sqrt($17*$17 + $19*$19)) w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"
    Phase diagram of the vertical and horizontal velocities (script)

    Phase diagram of the vertical and horizontal velocities (script)

    set xlabel "x"
set ylabel "z"
set zlabel "y"
set xyplane 0
set xrange [-5:2]
set yrange [-5:5]
set zrange [0:*]
splot "case-2/lmax-12/level-12.dat" u 14:16:(-($15-32)) w l lw 2 lc rgb "blue"      t "Basilisk, l=12", \
      "case-2/lmax-13/level-13.dat" u 14:16:(-($15-32)) w l lw 2 lc rgb "red"       t "Basilisk, l=13", \
      "case-2/lmax-14/level-14.dat" u 14:16:(-($15-32)) w l lw 2 lc rgb "sea-green" t "Basilisk, l=14"
    Time evolution of the particle trajectory (script)

    Time evolution of the particle trajectory (script)

    References

    [uhlman2005]

    M. Uhlman. An immersed boundary method with direct forcing for the simulation of particulate flows. Journal of Computational Physics, 209:448–476, 2005.
    [mordant2000]

    N. Mordant and J.-F. Pinton. Velocity measurement of a settling sphere. The European Physical Journal B, 18:343–352, 2000.